我对Android Things和蓝牙LE Gatt都很陌生。我尝试过Google提供的Bluetooth LE GATT server sample。我在Raspberry Pi 3和手机上的Android BluetoothLeGatt client sample上运行蓝牙LE GATT服务器示例。我在SampleGattAttributes.java中编辑了一些代码 BluetoothLeService.java。
SampleGattAttributes.java
public class SampleGattAttributes {
private static HashMap<String, String> attributes = new HashMap();
public static String CURRENT_TIME = "00002a2b-0000-1000-8000-00805f9b34fb";
public static String CLIENT_CONFIG = "00002902-0000-1000-8000-00805f9b34fb";
static {
// Sample Services.
attributes.put("00001805-0000-1000-8000-00805f9b34fb", "TIME SERVICE");
// Sample Characteristics.
attributes.put(CURRENT_TIME, "CURRENT TIME");}
BluetoothLeService.java
/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.bluetoothlegatt;
import android.app.Service;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothGatt;
import android.bluetooth.BluetoothGattCallback;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattDescriptor;
import android.bluetooth.BluetoothGattService;
import android.bluetooth.BluetoothManager;
import android.bluetooth.BluetoothProfile;
import android.content.Context;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;
import java.util.List;
import java.util.UUID;
/**
* Service for managing connection and data communication with a GATT server hosted on a
* given Bluetooth LE device.
*/
public class BluetoothLeService extends Service {
private final static String TAG = BluetoothLeService.class.getSimpleName();
private BluetoothManager mBluetoothManager;
private BluetoothAdapter mBluetoothAdapter;
private String mBluetoothDeviceAddress;
private BluetoothGatt mBluetoothGatt;
private int mConnectionState = STATE_DISCONNECTED;
private static final int STATE_DISCONNECTED = 0;
private static final int STATE_CONNECTING = 1;
private static final int STATE_CONNECTED = 2;
public final static String ACTION_GATT_CONNECTED = "com.example.bluetooth.le.ACTION_GATT_CONNECTED";
public final static String ACTION_GATT_DISCONNECTED = "com.example.bluetooth.le.ACTION_GATT_DISCONNECTED";
public final static String ACTION_GATT_SERVICES_DISCOVERED = "com.example.bluetooth.le.ACTION_GATT_SERVICES_DISCOVERED";
public final static String ACTION_DATA_AVAILABLE = "com.example.bluetooth.le.ACTION_DATA_AVAILABLE";
public final static String EXTRA_DATA = "com.example.bluetooth.le.EXTRA_DATA";
public final static UUID UUID_CURRENT_TIME = UUID.fromString(SampleGattAttributes.CURRENT_TIME);
// Implements callback methods for GATT events that the app cares about. For example,
// connection change and services discovered.
private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
@Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
String intentAction;
if (newState == BluetoothProfile.STATE_CONNECTED) {
intentAction = ACTION_GATT_CONNECTED;
mConnectionState = STATE_CONNECTED;
broadcastUpdate(intentAction);
Log.i(TAG, "Connected to GATT server.");
// Attempts to discover services after successful connection.
Log.i(TAG, "Attempting to start service discovery:" +
mBluetoothGatt.discoverServices());
} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
intentAction = ACTION_GATT_DISCONNECTED;
mConnectionState = STATE_DISCONNECTED;
Log.i(TAG, "Disconnected from GATT server.");
broadcastUpdate(intentAction);
}
}
@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
broadcastUpdate(ACTION_GATT_SERVICES_DISCOVERED);
} else {
Log.w(TAG, "onServicesDiscovered received: " + status);
}
}
@Override
public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
}
}
@Override
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
}
};
private void broadcastUpdate(final String action) {
final Intent intent = new Intent(action);
sendBroadcast(intent);
}
private void broadcastUpdate(final String action, final BluetoothGattCharacteristic characteristic) {
final Intent intent = new Intent(action);
// This is special handling for the Heart Rate Measurement profile. Data parsing is
// carried out as per profile specifications:
// http://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.heart_rate_measurement.xml
if (UUID_CURRENT_TIME.equals(characteristic.getUuid())) {
int flag = characteristic.getProperties();
int format = -1;
if ((flag & 0x01) != 0) {
format = BluetoothGattCharacteristic.FORMAT_UINT16;
Log.d(TAG, "Heart rate format UINT16.");
} else {
format = BluetoothGattCharacteristic.FORMAT_UINT8;
Log.d(TAG, "Heart rate format UINT8.");
}
final int heartRate = characteristic.getIntValue(format, 1);
Log.d(TAG, String.format("Received heart rate: %d", heartRate));
intent.putExtra(EXTRA_DATA, String.valueOf(heartRate));
} else {
// For all other profiles, writes the data formatted in HEX.
final byte[] data = characteristic.getValue();
if (data != null && data.length > 0) {
final StringBuilder stringBuilder = new StringBuilder(data.length);
for(byte byteChar : data)
stringBuilder.append(String.format("%02X ", byteChar));
intent.putExtra(EXTRA_DATA, new String(data) + "\n" + stringBuilder.toString());
}
}
sendBroadcast(intent);
}
public class LocalBinder extends Binder {
BluetoothLeService getService() {
return BluetoothLeService.this;
}
}
@Override
public IBinder onBind(Intent intent) {
return mBinder;
}
@Override
public boolean onUnbind(Intent intent) {
// After using a given device, you should make sure that BluetoothGatt.close() is called
// such that resources are cleaned up properly. In this particular example, close() is
// invoked when the UI is disconnected from the Service.
close();
return super.onUnbind(intent);
}
private final IBinder mBinder = new LocalBinder();
/**
* Initializes a reference to the local Bluetooth adapter.
*
* @return Return true if the initialization is successful.
*/
public boolean initialize() {
// For API level 18 and above, get a reference to BluetoothAdapter through
// BluetoothManager.
if (mBluetoothManager == null) {
mBluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
if (mBluetoothManager == null) {
Log.e(TAG, "Unable to initialize BluetoothManager.");
return false;
}
}
mBluetoothAdapter = mBluetoothManager.getAdapter();
if (mBluetoothAdapter == null) {
Log.e(TAG, "Unable to obtain a BluetoothAdapter.");
return false;
}
return true;
}
/**
* Connects to the GATT server hosted on the Bluetooth LE device.
*
* @param address The device address of the destination device.
*
* @return Return true if the connection is initiated successfully. The connection result
* is reported asynchronously through the
* {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
* callback.
*/
public boolean connect(final String address) {
if (mBluetoothAdapter == null || address == null) {
Log.w(TAG, "BluetoothAdapter not initialized or unspecified address.");
return false;
}
// Previously connected device. Try to reconnect.
if (mBluetoothDeviceAddress != null && address.equals(mBluetoothDeviceAddress) && mBluetoothGatt != null) {
Log.d(TAG, "Trying to use an existing mBluetoothGatt for connection.");
if (mBluetoothGatt.connect()) {
mConnectionState = STATE_CONNECTING;
return true;
} else {
return false;
}
}
final BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
if (device == null) {
Log.w(TAG, "Device not found. Unable to connect.");
return false;
}
// We want to directly connect to the device, so we are setting the autoConnect parameter to false.
mBluetoothGatt = device.connectGatt(this, false, mGattCallback);
Log.d(TAG, "Trying to create a new connection.");
mBluetoothDeviceAddress = address;
mConnectionState = STATE_CONNECTING;
return true;
}
/**
* Disconnects an existing connection or cancel a pending connection. The disconnection result
* is reported asynchronously through the
* {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
* callback.
*/
public void disconnect() {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w(TAG, "BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.disconnect();
}
/**
* After using a given BLE device, the app must call this method to ensure resources are
* released properly.
*/
public void close() {
if (mBluetoothGatt == null) {
return;
}
mBluetoothGatt.close();
mBluetoothGatt = null;
}
/**
* Request a read on a given {@code BluetoothGattCharacteristic}. The read result is reported
* asynchronously through the {@code BluetoothGattCallback#onCharacteristicRead(android.bluetooth.BluetoothGatt, android.bluetooth.BluetoothGattCharacteristic, int)}
* callback.
*
* @param characteristic The characteristic to read from.
*/
public void readCharacteristic(BluetoothGattCharacteristic characteristic) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w(TAG, "BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.readCharacteristic(characteristic);
}
/**
* Enables or disables notification on a give characteristic.
*
* @param characteristic Characteristic to act on.
* @param enabled If true, enable notification. False otherwise.
*/
public void setCharacteristicNotification(BluetoothGattCharacteristic characteristic,
boolean enabled) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w(TAG, "BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.setCharacteristicNotification(characteristic, enabled);
// This is specific to Heart Rate Measurement.
if (UUID_CURRENT_TIME.equals(characteristic.getUuid())) {
BluetoothGattDescriptor descriptor = characteristic.getDescriptor(UUID.fromString(SampleGattAttributes.CLIENT_CONFIG));
descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
mBluetoothGatt.writeDescriptor(descriptor);
}
}
/**
* Retrieves a list of supported GATT services on the connected device. This should be
* invoked only after {@code BluetoothGatt#discoverServices()} completes successfully.
*
* @return A {@code List} of supported services.
*/
public List<BluetoothGattService> getSupportedGattServices() {
if (mBluetoothGatt == null) return null;
return mBluetoothGatt.getServices();
}
}
单击当前时间时，它在数据字段中显示7。我可以知道数字7的来源以及为什么在我改变时间时没有通知。
答案 0 :(得分：2)
您从Android蓝牙LE客户端示例修改的代码可能会映射到正确的当前时间UUID，但它仍在尝试解析数据，就好像它是一个单一的心率测量broadcastUpdate()。
该方法中的代码是根据heart rate measurement规范解析数据字段，但来自服务器的数据是current time值。您的客户端代码需要根据蓝牙规范定义的当前时间解析该特性中的各个字节。
关于未调用onCharacteristicChanged()，您需要验证服务器是否实际收到了订阅请求。如果您希望看到注册发生，可以将日志记录添加到the server callback，每次收到更新事件时，服务器也会log a message触发向订阅者发送通知。